Collective bargaining means when a union (players) and company representative (in this case, the owners of the baseball teams) get together and negotiate over player's contracts and benefits.
In a negotiation, both sides will win some and lose some. So in this case, one of the agreement by the player's union was that the MLB will not release the testing results of 2003, since at the time, steroid wasn't deemed illegal in MLB.
Obviously someone couldn't keep their mouth shut.....